hi guys, eyewave here, with a discussion I'd like to light, can someone help my understanding of hypergamy theory?

Basically, what I understood is, mean women always are on a look-out for new higher/better partners, and honest good men can never rest easy that their committed relationship will last until death does them apart. Because, believe it or not, your girl will leave with another any opportunity she can grab, and then rinse and repeat until the end of times: even if in the process she's destroying things she might have built with the former partner like some wedding, or living in a house, or having children, doesn't matter, because she will always feel like she can "do better".

But wouldn't that mean women have no interest in being jealous, possessive, willing to settle down, hell some bros even call marriage being "tied down"! If women were so prompt to "monkey branch", why would they be so head over heels for becoming a wife. Like still in our times, weddings are still celebrated and girls look forward to it as soon as they can watch disney movies. And it is also known that men more often cheat than not, especially after a few years into married life have passed. And that cheating men severly damage psychologically the woman who's being cheated on.

I find it hard to conciliate that, any girl next-door I've chosen to marry is ready to leave me for another in a split second, but at the same time will want to tie me down and avoid being cheated on, sometimes in very toxic manner. I have heard a horror story of a friend of mine, once her best (male) friend has cut ties with her because his own girlfriend made him choose between them two. Doesn't seem very hypergamous to me.

tldr: If women are so prone to "monkey branch" as hypergamy says, why all the jealousy and interest in wedding and settling down? Is that all just fluff?

edit: thanks for the few reactions I have had. one more precision, I believe the hypergamy/monkey branching also implies that women's reason to leave were unreasonable. I personally don't blame a woman who needs to escape a wife-beater, or to sue a deadbeat father for pension.